Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $106.33   5.184%   $111.8421   $111.84   $111.85   $111.80  
  Purchase #2 $207.51   12.311%   $233.0566   $233.06   $233.05   $233.10  
  Purchase #3 $169.96   8.523%   $184.4457   $184.45   $184.45   $184.40  
  Purchase #4 $236.56   4.254%   $246.6233   $246.62   $246.60   $246.60  
  Purchase #5 $203.33   8.406%   $220.4219   $220.42   $220.40   $220.40  
  Purchase #6 $53.73   8.230%   $58.152   $58.15   $58.15   $58.20  
  Purchase #7 $59.54   6.691%   $63.5238   $63.52   $63.50   $63.50  
  7 purchase totals = $1,036.96       $1,118.0654   $1,118.06   $1,118.00   $1,118.00